In all anechoic chambers calibrating electronic equipment for radar cross section measurements, a reference target (reflecting surface) is necessary. Typically, a metal plate, sphere, or cylinder is used as such a reference target. The usual prior art approach is to mount such a reference target on a pylon downrange from a source of radar frequency energy and within the confines of an energy-absorbing or anechoic chamber.
In order to minimize any background interference from scattering, subtraction of the effect of the pylon and other surfaces within the chamber should be made. This means that separate measurements must be made with the reference target in place and with the reference target removed.
Typically, the supporting pylons are quite high so that the reference target is elevated well above the ground. Crane-type devices, such as cherry pickers, are used to position and remove a reference target on a supporting pylon during the many calibrations that are necessary during the testing of a radar system. A good majority of today's radar cross section measurement equipment require reference target and subtraction be done before moving on to the next calibration. If, for example, twelve calibrations are needed in a single day, 24 trips are required to install and remove the reference target. This can be extremely time consuming, especially in chambers with high and remote pylons.